In recent years, energy-saving measures have been taken significantly in view of environmental protection including the prevention of the greenhouse effect owing to carbon dioxide, although not so significantly as those during the oil crisis owing to oil shortage. Consumers of electric power are classified into industrial consumers and household consumers; the electric power consumption by the industrial consumers stays almost constant after 1970s, but the electric power consumption by the household consumers has increased twice or more after 1970s. Hence, additional energy-saving measures are required to be taken for household consumers.
At present, the great majority of electric power generated by electric power supplier sides, such as hydraulic, thermal and atomic electric power generation, is transmitted by a system comprising electric power transmission lines, substations, etc. and supplied to consumer sides, such as households and factories. In this kind of large electric power generation system, heat generating simultaneously with electric power generation cannot be used, and the loss of electric power transmission from electric power stations to consumers is large, whereby the final energy efficiency is low. Particularly in household consumers having many distributed loads with low amount of electric power consumption, energy efficiency becomes low.
For this reason, attention is paid recently to the so-called distributed electric power generation, that is, electric power generation by small-scale electric power generators near electric power consumption regions, and in particular, attention is paid to cogeneration-type electric power generation wherein electric power is generated by a gas turbine or a fuel cell and waste heat generated during electric power generation can also be used.
In this kind of distributed electric power generation, each of nodes, such as a household, a factory, a company, a building and a school, itself has an electric power generator, and the node purchases lacking electric power from an outside commercial electric power system (an electric power company, an electric power supplier or the like) and sells extran electric power to an electric power supplier, thereby performing the so-called “trading of electric power.”
Even in this kind of distributed electric power generation, if the sale of electric power to a commercial electric power system is carried out regardless of the present electric power demand, a transmission loss occurs in the case when a node that sells electric power is distant from an electric power supplier who purchases the electric power; however, conventionally, electric power should only be generated at one location and transmitted efficiently to locations near consumers; hence, if contractors who sell electric power are few, the transmission system is not affected greatly.
However, if each node sells extran electric power, transmission cost changes greatly depending on the distributions of electric power selling locations and electric power consuming locations. Accordingly, the present invention is intended to provide an electric power supply and demand management system capable of reducing the transmission loss and controlling and managing the supply and demand of electric power efficiently by selecting a node that can sell electric power from the electric power generator thereof the anode to an electric power supplier depending on the demand at the other nodes.
Furthermore, when a fuel cell is used as an electric power generator at the node, a time lag of at least one to two hours occurs until a fuel gas, such as hydrogen or propane gas, and oxygen are supplied to the fuel cell and then electric power generation starts. For this reason, when electric power is generated at a node, such as a dwelling house, wherein electric power demand greatly changes depending on time, season, or the like, the amount of electric power generated by the fuel cell cannot be controlled promptly depending on the change in the electric power demand at the node, whereby generated electric power becomes excessive or lacking. This causes a problem, that is, the above-mentioned node must purchase lacking electric power from the outside in spite of having an electric power generator or sell excessive electric power to the outside.
Accordingly, the present invention is intended to provide an electric power supply and demand management system capable of allowing a fuel cell used as an electric power generator to generate an appropriate amount of electric power, not excessive nor lacking, depending on the supply and demand at each node.